Some internal combustion engines include engine control systems that deactivate cylinders under low load situations. For example, an eight cylinder engine can be operated using four cylinders to improve fuel economy by reducing pumping losses. This process is generally referred to as displacement on demand (DOD). Operation using all of the engine cylinders is referred to as an activated mode. A deactivated mode refers to operation using less than all of the cylinders of the engine (i.e., one or more cylinders not active).
In the deactivated mode, there are fewer cylinders operating. As a result, there is less drive torque available to drive the vehicle driveline and accessories (e.g., alternator, coolant pump, A/C compressor). Engine efficiency, however, is increased as a result of decreased fuel consumption (i.e., no fuel supplied to the deactivated cylinders). Because the deactivated cylinders do not compress fresh air, pumping losses are also reduced.
A lifter oil manifold assembly (LOMA) is implemented to activate and deactivate select cylinders of the engine. The LOMA includes lifters and solenoids associated with corresponding cylinders. The solenoids are selectively energized to enable hydraulic fluid flow to the lifters to disable cylinder operation, thereby deactivating the corresponding cylinders. It is possible that one or more of the solenoids could seize or become slow to actuate and cause the system to operate improperly. As a result, the LOMA may need to be replaced.